This invention relates to a balancer shaft for a two cycle engine and more particularly to an improved and compact balancing arrangement for an internal combustion engine.
It is well known that reciprocating engines generate certain forces which should be balanced to provide smooth running. One way in which certain of these forces is balanced, is by providing a balancing shaft having eccentric masses which is driven from the engine crankshaft and which rotates at the same speed as the crankshaft but in an opposite direction. Although such balancing shafts have high utility and provide smooth running engines, the addition of a further shaft to the engine crankshaft complicates and enlarges the overall construction of the engine.
Conventionally it has been the practice to provide these balance shafts on the side of the engine crankshaft so as to avoid any increase in height of the overall engine. It is undesirable for a number of reasons to increase the height of the engine. Increasing the height of the engine not only raises the center of gravity of the engine in the overall vehicle but precludes the use of low hood lines which are important for aerodynamic reasons.
When a balancer shaft is employed with a two cycle, crankcase compression engine, additional problems arise. Normally it is the practice to induct air into the engine crankcase and if the balancer shaft also rotates in the crankcase, as is common practice, then the volume of the crankcase chamber becomes too large to permit effective compression. In addition, the added rotating operation of the balancer shaft in the crankcase can give rise to flows in the crankcase chamber that can adversely effect the induction system.
It is, therefore, a principal object to this invention to provide an improved balancer shaft arrangement for an internal combustion engine.
It is a further object to this invention to provide a balancer shaft arrangement for an engine that will not increase the overall height of the engine.
It is yet a further object to this invention to provide an improved balancer shaft arrangement for a two cycle, crankcase compression engine wherein the balancer shaft does not rotate within the crankcase chamber but is positioned closely adjacent the crankshaft.